Windows 8 was never (primarily) about driving PC sales for the
2012 holiday season. It’s a long bet on a future in which most
PCs have touch capability and many of them are tablets. As such,
any current conclusions about how it’s doing are hopelessly
premature.

But why put the touch/tablet UI on all PCs? A touch-optimized UI makes no more sense for a non-touch desktop than a desktop UI makes for a tablet. Apple has it right: a touch UI for touch devices, a pointer UI for pointer (trackpad, mouse) devices. Windows 8 strikes me as driven by dogma — “one Windows, everywhere”.